As high intensity discharge (HID) lighting fixtures are operated, electrical components housed therein are subjected to intense heat. Many such components are exposed to heat generated both by themselves and other components. This is true with regard to both the lamp itself and various electrical components located along the electrical path between the power source and the lamp.
In order to enhance fixture longevity and to avoid potential thermal damage of fixture components, the lighting fixture is traditionally designed and manufactured according to tolerances set with a view toward managing the thermal characteristics of the fixture components and the fixture interior in general. This is particularly true with regard to large HID industrial and commercial lighting fixtures used to illuminate streets, airports, stadiums, arenas, fields and other large light-critical spaces. One heat-sensitive fixture component that must be considered in the management of the thermal characteristics of the lighting fixture is the capacitor. In industrial and commercial lighting fixtures, capacitors are one of the larger electrical components, thereby occupying a substantial portion of the interior of the fixture and being exposed to substantial heat within the fixture. However, capacitors are quite heat-sensitive and have a relatively low maximum temperature rating. For instance, in a relevant industrial/commercial lighting fixture designed and manufactured by General Electric Company, the maximum operating temperature for the capacitor is set at 90 degrees Celsius, while the maximum operating temperature for the ballast of the same fixture are set at 165 to 180 degrees Celsius.
Traditionally, the capacitor is attached to and directly contacts the same support utilized by the ballast of the fixture. This arrangement results in significant heat transfer to the capacitor from the lamp and ballast, unacceptably low heat dissipation, and, ultimately, operation of the capacitor near or at its maximum operating temperature. One possible solution for maintaining the capacitor at a lower temperature during fixture operation is to enlarge the fixture to allow more airspace inside the fixture for greater heat dissipation. However, larger fixtures are more expensive to install, maintain, and replace than smaller fixtures, making fixture enlargement an economically inefficient solution.
Embodiments of the present invention address the concerns mentioned above through utilization of a resilient mount that maintains the capacitor itself in thermal contact with the interior wall of the fixture housing, thereby separating the capacitor from the other heat-generating electrical components in the fixture and maximizing capacitor heat dissipation through the fixture housing into ambient airspace.
In one aspect a lighting fixture is provided which includes a housing having an exterior wall with interior and exterior surfaces, a tray contained in the housing, at least one heat-sensitive component contained in the housing, and a mount secured to the tray supporting the heat-sensitive component, the mount maintaining the heat-sensitive component in thermal contact with the interior surface of the exterior wall of the housing, thereby facilitating dissipation of heat from the heat-sensitive component through the exterior wall of the housing.
In another aspect a method is provided for dissipating heat from a heat-sensitive component contained in a lighting fixture, said method including the steps of providing a lighting fixture comprising a housing having an exterior wall with interior and exterior surfaces, a tray contained in said housing, at least one heat-sensitive component contained in said housing, and a mount secured to said tray; attaching said heat-sensitive component to said mount; and orienting said tray in said housing such that said heat-sensitive component is maintained in thermal contact with said interior surface of said exterior wall of said housing.